1. Field of the Invention
The present invention pertains to maneuvering mechanisms for platforms, and in particular to maneuvering mechanisms for marine platforms. The present invention also pertains to a method for controlling a plurality of maneuvering mechanisms and to an apparatus for implementing said method.
2. Background and Relevant Information
Marine platforms are generally used for offshore drilling operations, and are provided with a plurality of supporting jacketlegs which are submerged at a chosen site and which rest on the ocean bottom in order to maintain the platform above sea level.
Control over the marine platform is carried out by means of a plurality of mechanisms which make it possible to raise, lower, and maintain the platform on its jacketlegs. These mechanisms consist of a reduction gear, driven by motorized means in two directions of rotation in order to permit the required movements of the platform and/or the jacketlegs. The gear motor is connected to the structure of the platform by an intermediary framework.
The maneuvering mechanisms comprise an output gear which meshes on a rack on a supporting jacketleg.
On each jacketleg, there are preferably at least two racks associated with different raising mechanisms.
The output gear of the reduction motor, more particularly the teeth of the output gear, receive loads originating from the platform or from the jacketlegs, through the intermediary of the corresponding rack. The output gears frequently work at their elastic limit. Significant variations in forces can lead to a breakdown of teeth on the output gear. Variations in forces can originate from excessive frictional stresses, or from the stripping of the jacketlegs during maneuvering.
Maneuvering mechanisms are known which allow the load applied to each of the output gears to be detected, as described in U.S. Pat. No. 4,587,854. These maneuvering mechanisms comprise means for measuring the torque borne by the output gear. The means are arranged directly on this output gear, and are associated with means for transmitting the value of the torque applied to the output gear. The output gear of the maneuvering mechanism is of the shafted type. That is, the output gear comprises a sheath capable of withstanding torsion between its two ends. The downstream end of the sheath comprises the output gear. The upstream end of the sheath is linked to the reduction gear.